Diarrhoea

Acute

For Gastro Causes

• Break down into parasitic, viral, bacterial:

  • Parasitic: Giardia, cryptosporidium

  • Viral: Enteric adenovirus, norovirus, rotavirus

  • Bacterial: C. difficile, Vibrio, B. cereus, Salmonella, Campylobacter, Shigella, ETEC

Giardia

• Watery, foul-smelling, greasy stools. Rotten egg burps. Float

• Viral: No fever, watery, no blood

• Bacterial: Fever, bloody stools

Clostridioides difficile (C. diff)

• Risk factors: cephalosporins, quinolones, prolonged hospital stay, PPI use

• Vibrio: Uncooked seafood

• Yersinia: Pigs

• B. cereus: Undercooked rice

• Salmonella & Campylobacter: Undercooked poultry, eggs

• Shigella: Raw salads

• ETEC: Undercooked meats

Non-Gastro Causes (Adults)

• Hyperthyroidism

• IBD (e.g., Crohn’s disease, ulcerative colitis)

• IBS

• Coeliac disease

• Ischaemic colitis

• SBO

• Constipation with overflow

• Lactose intolerance

Non-Gastro Causes (Kids)

• UTI

• Appendicitis

• Coeliac disease

• Constipation with overflow

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Chronic

• IBS

• IBD

• Coeliac disease

• Lactose deficiency

• Small intestinal bacterial overgrowth (SIBO)

• Giardia

Note: Consider microscopic colitis in older patients presenting with watery diarrhoea without blood, particularly those on NSAIDs

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Note:

• C. diff: Consider if antibiotics were used within 3 months or hospital stay >3 days

• SIBO: Decreased bowel transit → increased bacterial growth → diarrhoea

  • Increased risk with: Recent abdominal surgery, Crohn’s disease, diabetes

•  Chronic diarrhoea may require stool studies, faecal calprotectin (to differentiate IBD from IBS), and colonoscopy to identify inflammatory or neoplastic causes